Introduce veth_convert_xdp_buff_from_skb routine in order to
convert a non-linear skb into a xdp buffer. If the received skb
is cloned or shared, veth_convert_xdp_buff_from_skb will copy it
in a new skb composed by order-0 pages for the linear and the
fragmented area. Moreover veth_convert_xdp_buff_from_skb guarantees
we have enough headroom for xdp.
This is a preliminary patch to allow attaching xdp programs with frags
support on veth devices.
Signed-off-by: Lorenzo Bianconi <lorenzo@xxxxxxxxxx>
---
drivers/net/veth.c | 174 ++++++++++++++++++++++++++++++---------------
net/core/xdp.c | 1 +
2 files changed, 119 insertions(+), 56 deletions(-)
diff --git a/drivers/net/veth.c b/drivers/net/veth.c
index 22ecaf8b8f98..a45aaaecc21f 100644
--- a/drivers/net/veth.c
+++ b/drivers/net/veth.c
@@ -432,21 +432,6 @@ static void veth_set_multicast_list(struct net_device *dev)
{
}
-static struct sk_buff *veth_build_skb(void *head, int headroom, int len,
- int buflen)
-{
- struct sk_buff *skb;
-
- skb = build_skb(head, buflen);
- if (!skb)
- return NULL;
-
- skb_reserve(skb, headroom);
- skb_put(skb, len);
-
- return skb;
-}
-
static int veth_select_rxq(struct net_device *dev)
{
return smp_processor_id() % dev->real_num_rx_queues;
@@ -694,72 +679,143 @@ static void veth_xdp_rcv_bulk_skb(struct veth_rq *rq, void **frames,
}
}
-static struct sk_buff *veth_xdp_rcv_skb(struct veth_rq *rq,
- struct sk_buff *skb,
- struct veth_xdp_tx_bq *bq,
- struct veth_stats *stats)
+static void veth_xdp_get(struct xdp_buff *xdp)
{
- u32 pktlen, headroom, act, metalen, frame_sz;
- void *orig_data, *orig_data_end;
- struct bpf_prog *xdp_prog;
- int mac_len, delta, off;
- struct xdp_buff xdp;
+ struct skb_shared_info *sinfo = xdp_get_shared_info_from_buff(xdp);
+ int i;
- skb_prepare_for_gro(skb);
+ get_page(virt_to_page(xdp->data));
+ if (likely(!xdp_buff_has_frags(xdp)))
+ return;
- rcu_read_lock();
- xdp_prog = rcu_dereference(rq->xdp_prog);
- if (unlikely(!xdp_prog)) {
- rcu_read_unlock();
- goto out;
- }
+ for (i = 0; i < sinfo->nr_frags; i++)
+ __skb_frag_ref(&sinfo->frags[i]);
+}
- mac_len = skb->data - skb_mac_header(skb);
- pktlen = skb->len + mac_len;
- headroom = skb_headroom(skb) - mac_len;
+static int veth_convert_xdp_buff_from_skb(struct veth_rq *rq,
+ struct xdp_buff *xdp,
+ struct sk_buff **pskb)
+{
+ struct sk_buff *skb = *pskb;
+ u32 frame_sz;
if (skb_shared(skb) || skb_head_is_locked(skb) ||
- skb_is_nonlinear(skb) || headroom < XDP_PACKET_HEADROOM) {
+ skb_shinfo(skb)->nr_frags) {
+ u32 size, len, max_head_size, off;
struct sk_buff *nskb;
- int size, head_off;
- void *head, *start;
struct page *page;
+ int i, head_off;
- size = SKB_DATA_ALIGN(VETH_XDP_HEADROOM + pktlen) +
- SKB_DATA_ALIGN(sizeof(struct skb_shared_info));
- if (size > PAGE_SIZE)
+ /* We need a private copy of the skb and data buffers since
+ * the ebpf program can modify it. We segment the original skb
+ * into order-0 pages without linearize it.
+ *
+ * Make sure we have enough space for linear and paged area
+ */
+ max_head_size = SKB_WITH_OVERHEAD(PAGE_SIZE -
+ VETH_XDP_HEADROOM);
+ if (skb->len > PAGE_SIZE * MAX_SKB_FRAGS + max_head_size)
goto drop;
+ /* Allocate skb head */
page = alloc_page(GFP_ATOMIC | __GFP_NOWARN);
if (!page)
goto drop;
- head = page_address(page);
- start = head + VETH_XDP_HEADROOM;
- if (skb_copy_bits(skb, -mac_len, start, pktlen)) {
- page_frag_free(head);
+ nskb = build_skb(page_address(page), PAGE_SIZE);
+ if (!nskb) {
+ put_page(page);
goto drop;
}
- nskb = veth_build_skb(head, VETH_XDP_HEADROOM + mac_len,
- skb->len, PAGE_SIZE);
- if (!nskb) {
- page_frag_free(head);
+ skb_reserve(nskb, VETH_XDP_HEADROOM);
+ size = min_t(u32, skb->len, max_head_size);
+ if (skb_copy_bits(skb, 0, nskb->data, size)) {
+ consume_skb(nskb);
goto drop;
}
+ skb_put(nskb, size);
skb_copy_header(nskb, skb);
head_off = skb_headroom(nskb) - skb_headroom(skb);
skb_headers_offset_update(nskb, head_off);
+
+ /* Allocate paged area of new skb */
+ off = size;
+ len = skb->len - off;
+
+ for (i = 0; i < MAX_SKB_FRAGS && off < skb->len; i++) {
+ page = alloc_page(GFP_ATOMIC | __GFP_NOWARN);
+ if (!page) {
+ consume_skb(nskb);
+ goto drop;
+ }
+
+ size = min_t(u32, len, PAGE_SIZE);
+ skb_add_rx_frag(nskb, i, page, 0, size, PAGE_SIZE);
+ if (skb_copy_bits(skb, off, page_address(page),
+ size)) {
+ consume_skb(nskb);
+ goto drop;
+ }
+
+ len -= size;
+ off += size;
+ }
+
consume_skb(skb);
skb = nskb;
+ } else if (skb_headroom(skb) < XDP_PACKET_HEADROOM &&
+ pskb_expand_head(skb, VETH_XDP_HEADROOM, 0, GFP_ATOMIC)) {
+ goto drop;
}
/* SKB "head" area always have tailroom for skb_shared_info */
frame_sz = skb_end_pointer(skb) - skb->head;
frame_sz += SKB_DATA_ALIGN(sizeof(struct skb_shared_info));
- xdp_init_buff(&xdp, frame_sz, &rq->xdp_rxq);
- xdp_prepare_buff(&xdp, skb->head, skb->mac_header, pktlen, true);
+ xdp_init_buff(xdp, frame_sz, &rq->xdp_rxq);
+ xdp_prepare_buff(xdp, skb->head, skb_headroom(skb),
+ skb_headlen(skb), true);
+
+ if (skb_is_nonlinear(skb)) {
+ skb_shinfo(skb)->xdp_frags_size = skb->data_len;
+ xdp_buff_set_frags_flag(xdp);
+ } else {
+ xdp_buff_clear_frags_flag(xdp);
+ }
+ *pskb = skb;
+
+ return 0;
+drop:
+ consume_skb(skb);
+ *pskb = NULL;
+
+ return -ENOMEM;
+}
+
+static struct sk_buff *veth_xdp_rcv_skb(struct veth_rq *rq,
+ struct sk_buff *skb,
+ struct veth_xdp_tx_bq *bq,
+ struct veth_stats *stats)
+{
+ void *orig_data, *orig_data_end;
+ struct bpf_prog *xdp_prog;
+ struct xdp_buff xdp;
+ u32 act, metalen;
+ int off;
+
+ skb_prepare_for_gro(skb);
+
+ rcu_read_lock();
+ xdp_prog = rcu_dereference(rq->xdp_prog);
+ if (unlikely(!xdp_prog)) {
+ rcu_read_unlock();
+ goto out;
+ }
+
+ __skb_push(skb, skb->data - skb_mac_header(skb));
+ if (veth_convert_xdp_buff_from_skb(rq, &xdp, &skb))
+ goto drop;
orig_data = xdp.data;
orig_data_end = xdp.data_end;
@@ -770,7 +826,7 @@ static struct sk_buff *veth_xdp_rcv_skb(struct veth_rq *rq,
case XDP_PASS:
break;
case XDP_TX:
- get_page(virt_to_page(xdp.data));
+ veth_xdp_get(&xdp);
consume_skb(skb);
xdp.rxq->mem = rq->xdp_mem;
if (unlikely(veth_xdp_tx(rq, &xdp, bq) < 0)) {
@@ -782,7 +838,7 @@ static struct sk_buff *veth_xdp_rcv_skb(struct veth_rq *rq,
rcu_read_unlock();
goto xdp_xmit;
case XDP_REDIRECT:
- get_page(virt_to_page(xdp.data));
+ veth_xdp_get(&xdp);
consume_skb(skb);
xdp.rxq->mem = rq->xdp_mem;
if (xdp_do_redirect(rq->dev, &xdp, xdp_prog)) {
@@ -805,18 +861,24 @@ static struct sk_buff *veth_xdp_rcv_skb(struct veth_rq *rq,
rcu_read_unlock();
/* check if bpf_xdp_adjust_head was used */
- delta = orig_data - xdp.data;
- off = mac_len + delta;
+ off = orig_data - xdp.data;
if (off > 0)
__skb_push(skb, off);
else if (off < 0)
__skb_pull(skb, -off);
- skb->mac_header -= delta;
+
+ skb_reset_mac_header(skb);
/* check if bpf_xdp_adjust_tail was used */
off = xdp.data_end - orig_data_end;
if (off != 0)
__skb_put(skb, off); /* positive on grow, negative on shrink */
+
+ if (xdp_buff_has_frags(&xdp))
+ skb->data_len = skb_shinfo(skb)->xdp_frags_size;
+ else
+ skb->data_len = 0;
+
skb->protocol = eth_type_trans(skb, rq->dev);
metalen = xdp.data - xdp.data_meta;
@@ -832,7 +894,7 @@ static struct sk_buff *veth_xdp_rcv_skb(struct veth_rq *rq,
return NULL;
err_xdp:
rcu_read_unlock();
- page_frag_free(xdp.data);
+ xdp_return_buff(&xdp);
xdp_xmit:
return NULL;
}
diff --git a/net/core/xdp.c b/net/core/xdp.c
index 361df312ee7f..b5f2d428d856 100644
--- a/net/core/xdp.c
+++ b/net/core/xdp.c
@@ -528,6 +528,7 @@ void xdp_return_buff(struct xdp_buff *xdp)
out:
__xdp_return(xdp->data, &xdp->rxq->mem, true, xdp);
}
+EXPORT_SYMBOL_GPL(xdp_return_buff);
/* Only called for MEM_TYPE_PAGE_POOL see xdp.h */
void __xdp_release_frame(void *data, struct xdp_mem_info *mem)
--
2.35.1
